1. FIELD OF THE INVENTION
This invention relates to a data reproducing apparatus, and more particularly to an improvement of optical disc device which is utilized as an auxiliary memory unit for a computer.
2. DESCRIPTION OF THE RELATED ART
Heretofore, there is an optical disc device which is used as an auxiliary memory unit for a computer, etc.
In this optical disc device, there are optical disc devices for reproducing only which use-read-only optical discs and optical disc devices which use writable optical discs, such as magnetic optical discs and the like.
In these types of optical, disc devices, the content of an optical disc can be copied easily. Thus, a problem occurs regarding the protection of a copyrighted data.
Also, data representing the data structure of disc, DDS (Disc Definition Structure), is recorded in the optical disc. For example, the information for sector interchange-processing, etc. is recorded in the DDS.
The DDS is such important data as to be recorded twice each in the innermost and the outermost of an optical disc. If one DDS becomes impossible to error correct, the data structure can be obtained from another DDS recorded in another area.
However, even though the DDS is recorded four times, it may prove to be insufficient in some cases. This is a problem in that the optical disc can not be used when all DDS become impossible to error correct.